Mastigoteuthids are deep water pelagic or benthopelagic squids that are morphologically distinctive. They are weakly muscled, reddish in color and have elongate fourth arms and whip-like tentacular clubs. Much of the red pigment is not in chromatophore organs but dispersed in other integumental cells, although chromatophores are present. The Mastigoteuthidae, however, is among the most taxonomically confused families of all deep-sea squid due to the fact that many characters are based on the structures (tentacles and skin photophores) often lost during capture.
The whip-like tentacles have tentacular clubs that are little differentiated from the tentacular stalks eventhough they are covered with thousands of minute suckers. In some species, the suckers are so small as to be invisible to the naked eye. The photograph below shows the midregion of a tentacular club with the sucker-bearing portion marked by an X. The arrow points to a microscope enlargment showing the small suckers. Such small suckers, at least in freshly dead specimens, seem to function much like "fly paper" in that anything touching them, whether large or small, sticks.
Figure. Side view of a portion of the tentacle club (bottom) of Mastigoteuthis microlucens, Hawaiian waters, showing the club covering the top half of the cyclindrical tentacle. Insert - Portion of the club, marked by an "X", as seen through a microscope. Photographs by R. Young.
Fins are usually very large and positioned mostly posterior to the muscular part of the mantle. No well-developed system of giant nerve fibers is present, which reflects the absence of rapid jet propulsion (Dilly, et al., 1977).
Brief diagnosis:Member of the chiroteuthid families ...
- with arms IV longest.
- with cyclindrical, whip-like tentacular clubs bearing small suckers in numerous irregular series.
- with oval funnel locking-apparatus usually bearing various knobs or lobes (tragus and antitragus) affecting the shape of the groove.